All Pass 0b controls have pattern_id=NULL. Rewritten to:
- Phase 1: Group by merge_group_hint (action:object:trigger), 52k groups
- Phase 2: Cross-group embedding search for semantically similar masters
- Qdrant search uses unfiltered cross-regulation endpoint
- API param changed: pattern_id → hint_filter
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>